#include <iostream>
#include <functional>

struct wrap
{
	std::function<wrap ()> f;
	template<typename F>
	wrap(F f)
	: f(f)
	{
	}
	wrap operator()()
	{
		return f();
	}
};

wrap menu_sub_1();
wrap menu_sub_2();
wrap menu_main()
{
	std::cout
		<< "Main menu" << std::endl
		<< "1. Sub menu 1" << std::endl
		<< "2. Sub menu 2" << std::endl
		<< "3. Exit" << std::endl;
	int x;
	std::cin >> x;
	if(x == 1) return menu_sub_1;
	else if(x == 2) return menu_sub_2;
	else if(x == 3) std::exit(0);
	return menu_main;
}
wrap menu_sub_1()
{
	std::cout
		<< "Sub menu 1" << std::endl
		<< "1. Back to main menu" << std::endl;
	int x;
	std::cin >> x;
	if(x == 1) return menu_main;
	return menu_sub_1;
}
wrap menu_sub_2()
{
	std::cout
		<< "Sub menu 2" << std::endl
		<< "1. Back to main menu" << std::endl;
	int x;
	std::cin >> x;
	if(x == 1) return menu_main;
	return menu_sub_2;
}

int main()
{
	auto f = menu_main();
	while(true)
	{
		f = f();
	}
}